1. Field of the Invention
The present invention relates to a lens device mounted on a video camera or a television camera. In particular, the present invention relates to a lens device, which has both of an operation tool that manually operates an aperture stop device so as to adjust an amount of incident light and an operation tool that manually adjusts an amount of transmitted light of a variable light transmission filter, and an imaging device mounted with the lens device.
2. Description of the Related Art
As the device that adjusts the amount of incident light, an aperture stop (iris) device is generally used. For example, an aperture stop device 100 shown in FIG. 17 is configured such that a plurality of (six, in the example shown in the drawing) aperture stop blades 101, which functions as an iris, is disposed on a circumference and a driving point 102 of each blade 101 is moved in a direction of an arrow 104 centered on a supporting point 103 so as to decrease an aperture area (aperture size) of a center hole 105 which transmits incident light.
In the aperture stop device 100, when the amount of incident light is intended to be decreased, the center hole 105 is narrowed. However, when a bright outdoor image is photographed at a minimum aperture position, blurring which is caused by a decrease in a resolving power decreased by the effect of the diffraction phenomenon, so-called small aperture blurring may occur, and may deteriorate a quality of a photographed image.
For this reason, as the device that adjusts the amount of incident light, for example, an ND filter disclosed in JP2007-243928A to be described later has been proposed. The ND filter is formed as a discoid filter in which a density of a dimming material continuously changes along the circumference. In addition, by adjusting the rotation position of the discoid filter, the amount of transmitted light of the filter is controlled.
Further, a light amount adjustment device disclosed in JP2006-126504A has been proposed. In the light amount adjustment device, electrodes are provided on both surfaces of a discoid dielectric elastomer placed on the optical path, a voltage applied between the electrodes is adjusted, and a thickness of the discoid film is controlled, thereby realizing the ND filter of which the amount of transmitted light is variable.
By inserting the variable light transmission filter exemplified in JP2007-243928A and JP2006-126504A into the aperture stop device shown in for example FIG. 17, it is possible to avoid occurrence of small aperture blurring even when photographing the bright outdoor image. However, in the variable light transmission filter, it is difficult to perform imaging that blurs the background through adjustment of the depth of field performed by adjusting the aperture stop diameter, the adjustment being regarded as an advantage of the aperture stop device.
That is, both the aperture stop device and the variable light transmission filter are able to adjust the amount of incident light, but both have advantages and disadvantages for other functions.
For this reason, as disclosed in the following JP-H09-186922A and JP-H05-292392A, imaging devices, which use both the aperture stop device and the variable light transmission filter (variable ND filter) in combination, have been proposed. In such imaging devices, it is possible to perform appropriate exposure in any imaging condition, it is also possible to avoid small aperture blurring, and it is also possible to adjust the depth of field. However, since costs increase in order to mount two light amount adjustment means, it is difficult to apply the above-mentioned configuration to an actual device.